Slann has access to mad leaping all over the board. Underworld has mutations on goblins. The third new team is Chaos Pact, and is the final team of the new three that the GLN wanted to cover. Yet, what is so special about Chaos Pact exactly?

Three Big Guys

If we compare Chaos Pact to regular Chaos – which could be argued to be closest to Chaos Pact both in roster and fluff – Chaos Pact has access to two more Big Guys. While we all know that Big Guys should always be used as massive roadblocks, having access to three means that the road can be totally jammed sometimes. In other words, those Big Guys are very useful, as long as they attract as much attention as possible.
Because they also have to 'replace' the lack of STR 4 (Chaos Warriors) on the team. And I am reasonably sure that most of you coaches would prefer two Chaos Warriors to a Minotaur/Ogre and a Lineman.

The Renegades

Alright, alright. The Big Guys might not be worth enough to pick Chaos Pact as your team to play with. However, the team can also field three renegades. A Dark Elf, a Skaven and a Goblin. They are all just linemen with Animosity though, so how good can that be? It depends. The renegades are perhaps not incredibly attracting, they do open some options for the team. Let's see!
The Goblin might look useless at first, but his presence on the team is certainly good for something: throw him with a Big Guy for a last-turn One-Turn Touchdown. In addition, you can give him Sneaky Git for some low-risk strategic fouling. Finally, the little bugger has Mutation access, which makes his future bright. A Two Heads, Horns, Big Hand goblin can steal a ball when you'd least expect it.
The Dark Elf might just be a Lineman looking at his stats, but as a AG 4 player on a relatively bashy roster, he is much more. Some might be tempted to use him as a thrower due to the AG 4, but that isn't very wise due to the Animosity skill. He is definitely a ball carrier though. You should either use him as a protected runner – you can trust him with his AG 4 to pick the ball up easily as well as dodge out of a tight situation if necessary – or as a receiver. Either way, he is probably going to rack up quite some SPPs, and that makes him even more useful. Besides Block and Dodge for protection, his Mutation access combined with AG 4 means you can make a Leap/Very Long Legs player or give him Big Hand and Two Heads so that he can take the ball in any situation.
The Skaven might very well be the worst of the three on the roster. A player with MA 7 on a team that isn't oriented for speed isn't all that useful. He can be used as a speedy receiver, which is especially useful if you need to score in a two-turn drive. The other option is to make him into the team's Dirty Player, as he can get to and from his targets just a little faster. Some coaches might opt not to include him on the team though. However, with some development he can be quite good at his role, thanks to Extra Arms and Two Heads. Still, the Skaven will only really shine if you happen to roll a stat increase with him.
So yes, the three renegades definitely add something to the team. But enough to warrant no STR 4 players? Enough to make you want to play the team?

The Prototype: Marauder

Yes, you might like having three brutal Big Guys. You might appreciate the three renegades and their differing talents. Yet the key to growing your Chaos Pact team to full potential is the fact that the team fields the perfect lineman. And here is why the Marauder is so good. The Marauder is almost exactly like the Human Lineman. A clean, standard statline: 6/3/3/8 without any skills. For 50K, that's decent. You will rarely hear someone complain about the value for money on Human Linemen. No, they aren't all that good, but they are worth their money. They fill their role perfectly. What the Marauder offers, is skill access to Passing, Strength AND Mutation WITHOUT any increase in TV. That's exciting for more than one reason.
Under the new rules, a double is worth 10K more than a regular skill. This means that on a high TV Chaos Pact team, Marauders can take Passing, Strength and Mutation skills for lower than other teams do. Marauders are incredibly TV-efficient. That might not sound all too jolly, but its implications are huge. You should only very rarely take an Agility skill - probably Jump Up or Dodge are the only interesting skills, and only for specific players. Jump Up is good in combination with Mighty Blow, Piling On and Claw for a brutal, mobile pain bringer and Dodge has its uses on a stat freak you want to keep alive and useful at all times. At other times, stick to the wide array of other skills. Block and Guard should be the standard, with a few Claw and Mighty Blow players to hit hard. A dedicated thrower with Sure Hand, Pass and Accurate opens up the passing play with a renegade as receiver. Finally, a few players with Wrestle and Tackle fill the role of disturbing the opponent's game plan.
Distribute your Mutations smartly. A player with a STR increase love his Tentacles and Foul Appearance, a player with an AG increase could be complimented with Two Heads, Extra Arms and Big Hand to be an all-round ball player. Of course, you can always have a little fun with one Mutation-spammed player!

So, these three elements make up the Chaos Pact team. If, however, it is the Big Guy power aspect that solely piques your interest, than you should turn to Khemri, Lizardmen or regular Chaos. What Chaos Pact is really all about, is options and possibility! Marauders are incredibly efficient and can turn into all-round monsters, especially thanks to the Big Guy roadblocks. Add in a OTT Goblin, a Skaven runner-receiver and a mutating Dark Elf and you have got a team that can perform surprisingly well. Remember though, at its core Chaos Pact is a control-bashy team. Roadblocks and STR access means you have to go for the blocking route, and often a slow grind. The difference with many similar teams is that Chaos Pact has more alternatives due to its many options. It can open up a passing play if there is not a lot of time left, or it can throw a goblin for a lucky OTT. The team can field a plethora of different options if the classic control-bash-grind does not work, but it requires a handy coach to balance all these options without losing much efficiency in the standard strategy.